The present invention relates to a low turbulence airflow sensor. Airflow sensors are known in the prior art. However, Applicant is unaware of any such device including all of the features and aspects of the present invention.
The following prior art is known to Applicant:
U.S. Pat. No. 3,685,355 to DeBaun discloses an air monitoring system wherein the airflow sensor includes radially outwardly extending arms with each arm having a plurality of perpendicularly disposed sensing tubes attached thereto. These sensing tubes are spaced such that the radial distance between adjacent sensing tubes decreases as the location of the sensing tubes increases relative to the center of the conduit so that "each sensor is so positioned as to lie approximately at the center of a cross-sectional segment of the casing that is equal in area to the cross-sectional casing segment within which each of the other sensors is centered". However, DeBaun fails to take steps to minimize turbulence in the region where the air sensor is located. DeBaun utilizes the perpendicular sensing tubes which, in conjunction with the radially outwardly extending arms, contribute to increased turbulence. The central hub of DeBaun is not designed in any way to reduce turbulence nor is the design of the connection points between the radially outwardly extending arms and the inner walls of the casing so designed. In contrast, in the present invention, thin profile radially outwardly extending sensing arms are provided extending outwardly from a streamlined central hub and extending radially outwardly to streamlined connection devices.
U.S. Pat. No. 4,297,900 to Brandt, Jr. discloses an averaging pitot primary system which utilizes radially outwardly extending sensing arms having enlarged shrouds surrounding each pitot tube. Again, Brandt, Jr. appears to make no effort to reduce turbulence around and about the airflow sensor.
U.S. Pat. No. 4,344,330 to Renken et al. discloses an average fluid flow sensor which is made up of either a circular sensing tube or a spiral sensing tube. The present invention differs from the teachings of Renken et al. as providing a streamlined low turbulence airflow sensor which consists of a plurality of radially outwardly extending airflow sensors which extend between streamlined connection points.
U.S. Pat. No. 4,372,171 to Brandt, Jr. discloses a nozzle pitot averaging primary which utilizes a plurality of radially outwardly extending tubes having their respective ends facing toward air flow to allow receipt of air flow therein. Brandt, Jr. fails to contemplate the streamlining of the present invention nor the structure for ensuring that each tube receives air from radially spaced concentric circles of equal area.
U.S. Pat. No. 4,453,419 to Engelke discloses a device for sensing the volummetric flow rate of air in a duct which includes the provision of radially outwardly extending arms having equally spaced openings therein. The flow sensing tubes extend outwardly from a somewhat streamlined central hub. Upstream and downstream sensing tubes are separated by flattened, enlarged walls. These flattened and enlarged walls increase the turbulence around the airflow sensor in a manner not contemplated by the present invention. Furthermore, the conical nature of the surfaces of the central hub of Engelke and the stepped surfaces thereof are inferior to the slightly rounded air foil shape of the central hub of the present invention.
U.S. Pat. No. 4,602,514 to Kurrle et al. discloses a device for measuring the volume of flow of gas in a duct which includes the use of a plurality of radially outwardly extending sensing tubes with the openings in the sensing tubes being arranged radially in a logarithmic pattern. Furthermore, the sensing tubes are formed of square cross-section. While the logarithmic pattern of the entrance ports of the sensing tubes is generally related to the teachings of the present invention, Kurrle et al. do not take advantageous steps to reduce turbulence around and about the airflow sensing tubes as is the case in the present invention.
U.S. Pat. No. 4,735,100 to Hajto discloses a fluid flow sensor having multiplying effect which includes forward and rearward facing airflow sensing devices extending linearly across a rectangular cross-section duct and separated by enlarged vertical walls. The present invention differs from the teachings of Hajto as providing improvements to reduce turbulence in and around the airflow sensor and as being particularly designed for use in a conduit of circular cross-section.
U.S. Pat. No. 4,912,973 to Milewski et al discloses a multiple point velocity probe wherein a plurality of radially outwardly extending and bent airflow sensing tubes are provided, with each airflow sensing tube having a plurality of equally spaced air receiving ports therein. The airflow sensing tubes extend outwardly from a central generally rectangular cubic hub. The present invention differs from the teachings of Milewski et al. as contemplating a central hub of air foil shape to reduce turbulence and spacing of the airflow sensor openings in a manner that each opening receives air from an area equal to the area which supplies air to the other openings.
U.S. Pat. No. 5,123,288 to Tench et al. discloses an averaging pitot probe having a single airflow sensing tube extending across a circular duct. As described, each of the holes lies on the boundary between adjacent areas within the conduit, however, the spacing between the openings is not designed in the manner of the present invention, to-wit, to ensure that air flow to each hole is from a region of equal area to the areas which supply air to the other holes.